1. Field of the Invention
The present invention relates to an instant film pack and an instant camera. More particularly, the present invention relates to an improvement of an instant film pack and an instant camera in which instant film units can be reliably protected from ambient light.
2. Description Related to the Prior Art
An instant camera is known as capable of producing a photograph as soon as it is taken, in fashion without complicated steps of photofinishing for ordinary photography. The instant camera has a film pack loading chamber, which is open to a rear of the camera and appears when a back lid is opened. The loading chamber is loaded with an instant film pack, of which a plastic case contains a number of film units of a self-processing type stacked together. On a back wall of the film pack is mounted a pressure plate constituted by a metallic plate spring, which presses a rear of the film units. When a photograph is taken, one of the film units is exited through an outlet slot in a top of the camera, by a claw mechanism incorporated in the camera for ejecting the film unit from the case. During the ejection, spreading rollers squeeze the film unit, press processing solution out of a solution pod, and spread it over a photosensitive image-recording portion of the film unit. A photographic image is gradually formed on the image-recording portion. In the film pack another film unit next to be exposed is pressed by the pressure plate and positioned directly behind the exposure aperture.
As illustrated in FIG. 36, the instant film pack has a plastic case 2 and film units 12. The case 2 consists of a casing frame 2a and a back wall 2b, and has an exposure aperture 4 formed in the casing frame 2a. The casing frame 2a has a cutout 6 which communicates the exposure aperture 4, and adapted to receiving a claw device 5 of the camera for ejecting the film units 12 after exposure. Through an outlet slot 7, the film units 12 are exited. A metallic clip 8 is fitted on a top of the casing frame 2a, and reinforces the outlet slot 7. A metallic pressure plate 9 is secured to the back wall 2b, and has a springy characteristic provided by plural slits and the finishing with bending. The springy characteristic of the pressure plate 9 presses the film units 12 toward the exposure aperture 4, for the purpose of flattening the film units 12. FIG. 37 illustrates another conventional film pack, including a case 232, a clip 236 and a pressure plate 237.
The instant film pack is contained in the instant camera. When all the film units of the film pack are exposed, the film pack is removed from the camera, and discarded as incombustible waste.
The film pack to be discarded, however, has both plastic parts including the case 2 and metallic parts including the pressure plate 9 and the clip 8. The disposal of the plastic and metallic parts as assembled is undesirable in view of protection of environment. To separate the metallic parts from the plastic parts requires destruction of the case. Accordingly the disposal or recycling of the parts are excessively costly, particularly for collectively withdrawn film packs treated in huge scale. The disposal and recycling of the film pack is completely inconsistent to the actually practiced mass production of the film packs. Another problem lies in the metallic pressure plate 9 which is costly to be manufactured and raises the cost of the film pack, in addition to rise in its weight.
JP-U 63-150954 illustrates an instant camera having a pressure plate, which is disposed on the back lid. A film pack has an access opening for receiving the pressure plate, and a resilient light-shielding sheet attached to the access opening for preventing ambient light from entering the film pack through the access opening. U.S. Pat. No. 4,823,155 illustrates a similar a pressure plate, which is disposed on the back lid, and has a characteristic of increasingly changing the height toward the film units with the decrease of the film units in the film pack, so as to press the foremost one of the film units against the exposure aperture.
The use of the film pack as disclosed in JP-U 63-150954 or U.S. Pat. No. 4,823,155 may eliminate the metallic pressure plate. However this brings another problem in failure in shielding light through the exposure aperture. When the unused film pack is inserted into the instant camera, a user's fingers are likely to touch a light-shielding cover disposed in front of the film units and behind the exposure aperture, and depress the film units toward the back lid. Peripheral gaps take place between the exposure aperture and the light-shielding sheet, and introduce ambient light into the case to fog the film units. There is a difference in thickness between the middle and the periphery of the film unit, because the solution pod is disposed on an edge close to the outlet slot, and a trap portion is disposed on an opposite edge for absorbing surplus solution. The middle of the film units is likely to be depressed, to fog the film units.
The pressure plate in the camera of JP-U 63-150954 or U.S. Pat. No. 4,823,155 is so small that only the middle of the film units in contact with the film units is reliably pressed against the exposure aperture. There is a problem in that pressure to peripheral portions of the film units is insufficient. The trap-side edge of the film units to be engaged with the claw device of the camera is likely to fail to engage. Thus the ejection of the film units is unstable. The pod-side edge is also involved with a problem in being received in the outlet slot.
If a similar pressure plate is enlarged to cover the trap-side edge and the pod-side edge of the film units, a camera will be given much greater weight. The solution pod may be accidentally ruptured by the enlarged pressure plate before exposure. The image-recording portion is likely to be given "pressure fogging". An access opening, which is formed in the film pack for receiving the pressure plate of the camera, is obliged to have an enlarged size, to pose a problem in capacity of the film pack in shielding the film units from ambient light.
The pressure plate disclosed in JP-U 63-150954 or U.S. Pat. No. 4,823,155 has another problem in that its portions are likely to engage accidentally with the film pack during the loading into the loading chamber, in addition to the poor appearance of the pressure plate when the back lid is opened.